pysandbox 1.5 released

Victor Stinner victor.stinner at
Tue Mar 20 13:32:43 CET 2012

pysandbox is a Python sandbox. By default, untrusted code executed in
the sandbox cannot modify the environment (write a file, use print or
import a module). But you can configure the sandbox to choose exactly
which features are allowed or not, e.g. import sys module and read
/etc/issue file.

Main changes since pysandbox 1.0.3:

 - More modules and functions are allowed: math, random and time
modules, and the compile() builtin function for example
 - Drop the timeout feature: it was not effective on CPU intensive
functions implemented in C
 - (Read the ChangeLog to see all changes.)

pysandbox has known limitations:

 - it is unable to limit memory or CPU
 - it does not protect against bugs (e.g. crash) or vulnerabilities in CPython
 - dict methods able to modify a dict (e.g. dict.update) are disabled
to protect the sandbox namespace, but dict[key]=value is still

It is recommanded to run untrusted code in a subprocess to workaround
these limitations. pysandbox doesn't provide an helper yet.

pysandbox is used by an IRC bot (fschfsch) to evaluate a Python
expression. The bot uses fork() and setrlimit() to limit memory and to
implement a timeout.


The limitation on dict methods is required to deny the modification of
the __builtins__ dictionary. I proposed the PEP 416 (frozendict) but
Guido van Rossum is going to reject it. I don't see how to fix this
limitation without modifying CPython.


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